The interplay between deformation and magma transport in southeast Iceland
Igneous intrusions are of fundamental importance to society's ability to source critical metals, predict major natural hazards and, understand how Earth’s crust evolved. However, the factors that control how magma transits through Earth’s crust and the variables that determine if magma will arr...
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| Other Authors: | , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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The University of St Andrews
2023
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| Online Access: | http://hdl.handle.net/10023/27086 https://doi.org/10.17630/sta/318 |
| Summary: | Igneous intrusions are of fundamental importance to society's ability to source critical metals, predict major natural hazards and, understand how Earth’s crust evolved. However, the factors that control how magma transits through Earth’s crust and the variables that determine if magma will arrest during the process of ascent or erupt at the surface remains a challenge. This study investigates the interface between key tectonic, host rock and magma parameters to advance our understanding of how these variables influence magma transport processes in sub-volcanic plumbing systems. Specifically, this thesis assesses the interplay of magma flow dynamics and i) deformation structures associated with the ambient extensional stress regime of SE Iceland and ii) host rock deformation processes caused by the process of laccolith intrusion. The first part of the thesis investigates how surface and overburden deformation (forced folds, faults, and fractures) correlate with the mechanism of magma emplacement. In a case study on the Sandfell Laccoith, eastern Iceland, this chapter presents new palaeomagnetic data and a modified fold test to assess the formation of a forced fold. The results show that the formation of the forced fold occurred in two distinct processes that required the temporal break between the initial injection of magma and the later inflation of the laccolith. An evolutionary model is proposed whereby the continuous forceful emplacement of magma involved initial lateral propagation of a sill-like body preferentially towards the SSW resulting in forced folding with a relatively simple geometry. Continuous addition of magma at the base of the laccolith resulted in subsequent ‘bulldozing’ of magma underlying the cooled, viscously stalled initial magma. Magma that was subsequently injected into the laccolith caused inflation facilitated by further displacement of host rock and the formation of a prominent forced fold that is today observed in outcrop. This study demonstrates the utility of a new modified fold ... |
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